Most pipe bending machines used to bend large diameter pipe have similar principles of operation. Three bending shoes are provided. Usually there are two lower bending shoes in spaced relation which support the pipe and one upper bending shoe positioned above the pipe at an intermediate position between the two lower bending shoes. Relative movement of the bending shoes toward each other results in a force being exerted to bend the pipe. U.S. Pat. No. 5,353,622 which was issued to Theener in 1994 illustrates such a pipe bending machine.
In order to bend large diameter pipe, there is usually required a number of other machines on site, in addition to the pipe bending machine. Lifting equipment is required in order to lift the large diameter pipe on and off the pipe bending machine and move the pipe laterally through the pipe bending machine as the pipe is being bent. In addition, the pipe must be supported as it is being bent. If not properly supported, the pipe has an increasing tendency to twist as the bend progresses.